I had the cat removed and Moto Corse midpipe added a week ago at the 1000km service. This morning I came to work on the Brutale, and I think it does make an appreciable difference. It's definitely louder. Sounds better to me.

Of course I'm now exploring a much higher rev range than I was before...but it seems to have a little bit more umph (read: power). And it sounds fantastic up towards 10k!

I installed the Arrow mid pipe & carbon exhaust. The guys at Arrow's say the mid pipe slightly restricts the air flow and as a result the power is reduced by a few HP around 10,000rpm. They say that a new fuel map is required to balance and then a slight increase could be recognized.

I do not notice any loss (or increase) of power, it makes a little more noise & if I remove the baffels it sounds much improved.

Still however it sounds like an out board boat motor no matter what we do to it. Too bad with Ferarri doing engine development and the attention they pay to exhaust note you would think the 910 would sing.

Yeah, it seems the consensus is that mapping is afr more impotant than the pipes, as they are already very good.
I plan to reomove mine, but primarily so I can have the headers and midpipe ceramic coated to reduce heat.